2.7. Adaptation is a Necessary Strategy at All Scales to Complement Climate
Change Mitigation Efforts

Adaptation has the potential to reduce adverse impacts of climate change and
to enhance beneficial impacts, but will incur costs and will not prevent all
damages. Extremes, variability, and rates of change are all key features in
addressing vulnerability and adaptation to climate change, not simply changes
in average climate conditions. Human and natural systems will to some degree
adapt autonomously to climate change. Planned adaptation can supplement autonomous
adaptation, though options and incentives are greater for adaptation of human
systems than for adaptation to protect natural systems. Adaptation is a necessary
strategy at all scales to complement climate change mitigation efforts. [6]

Experience with adaptation to climate variability and extremes can be drawn
upon to develop appropriate strategies for adapting to anticipated climate change.
Adaptation to current climate variability and extremes often produces benefits
as well as forming a basis for coping with future climate change. However, experience
also demonstrates that there are constraints to achieving the full measure of
potential adaptation. In addition, maladaptation, such as promoting development
in risk-prone locations, can occur due to decisions based on short-term considerations,
neglect of known climatic variability, imperfect foresight, insufficient information,
and over-reliance on insurance mechanisms. [6]

2.8 Those with the Least Resources have the Least Capacity
to Adapt and are the Most Vulnerable

The ability of human systems to adapt to and cope with climate change depends
on such factors as wealth, technology, education, information, skills, infrastructure,
access to resources, and management capabilities. There is potential for developed
and developing countries to enhance and/or acquire adaptive capabilities. Populations
and communities are highly variable in their endowments with these attributes,
and the developing countries, particularly the least developed countries, are
generally poorest in this regard. As a result, they have lesser capacity to
adapt and are more vulnerable to climate change damages, just as they are more
vulnerable to other stresses. This condition is most extreme among the poorest
people. [6.1; see also 5.1.7,
5.2.7, 5.3.5, 5.4.6,
5.6.1, 5.6.2, 5.7,
and 5.8.1 for regional-scale information]

Benefits and costs of climate change effects have been estimated in monetary
units and aggregated to national, regional, and global scales. These estimates
generally exclude the effects of changes in climate variability and extremes,
do not account for the effects of different rates of change, and only partially
account for impacts on goods and services that are not traded in markets. These
omissions are likely to result in underestimates of economic losses and overestimates
of economic gains. Estimates of aggregate impacts are controversial because
they treat gains for some as canceling out losses for others and because the
weights that are used to aggregate across individuals are necessarily subjective.
[7.2.2 and 7.2.3]

Notwithstanding the limitations expressed above, based on a few published estimates,
increases in global mean temperature9
would produce net economic losses in many developing countries for all magnitudes
of warming studied (low confidence6),
and losses would be greater in magnitude the higher the level of warming (medium
confidence6).
In contrast, an increase in global mean temperature of up to a few °C would
produce a mixture of economic gains and losses in developed countries (low 6),
with economic losses for larger temperature increases (medium confidence6).
The projected distribution of economic impacts is such that it would increase
the disparity in well-being between developed countries and developing countries,
with disparity growing for higher projected temperature increases (medium confidence6).
The more damaging impacts estimated for developing countries reflects, in part,
their lesser adaptive capacity relative to developed countries. [7.2.3]

Further, when aggregated to a global scale, world gross domestic product (GDP)
would change by ± a few percent for global mean temperature increases
of up to a few °C (low confidence6),
and increasing net losses would result for larger increases in temperature (medium
confidence6)
(see Figure SPM-2). More people are projected
to be harmed than benefited by climate change, even for global mean temperature
increases of less than a few °C (low confidence6).
These results are sensitive to assumptions about changes in regional climate,
level of development, adaptive capacity, rate of change, the valuation of impacts,
and the methods used for aggregating monetary losses and gains, including the
choice of discount rate. [7.2.2]

The effects of climate change are expected to be greatest in developing countries
in terms of loss of life and relative effects on investment and the economy.
For example, the relative percentage damages to GDP from climate extremes have
been substantially greater in developing countries than in developed countries.
[4.6]

2.9. Adaptation, Sustainable Development, and Enhancement
of Equity can be Mutually Reinforcing
Many communities and regions that are vulnerable to climate change are also under
pressure from forces such as population growth, resource depletion, and poverty.
Policies that lessen pressures on resources, improve management of environmental
risks, and increase the welfare of the poorest members of society can simultaneously
advance sustainable development and equity, enhance adaptive capacity, and reduce
vulnerability to climate and other stresses. Inclusion of climatic risks in the
design and implementation of national and international development initiatives
can promote equity and development that is more sustainable and that reduces vulnerability
to climate change. [6.2]